Conductor



March 4, 941 F2, J, Wasi-:MAN

CONDUCTOR Filed Nov. 2, 1.929.

IN V EN TOR.

BY v z'yww M ATTORNEYS.` e

Patented Mar. 4, 1941 UNITED STATES CONDUCTOR Robert J. Wiseman, Passaic, N. J., assignor to The Okonite Company, Passaic, N. J., a corporation of New Jersey Application November 2, 1929, Serial No. 404,245

9 Claims.

This invention relates to an improvement in electric cables, andhas for one of its objects the provisions of a covering for the electrical insulation of the cable whereby electrical de- 5 terioration of the insulation will be reduced to a minimum.

It is well known in the art of electric cables that when the insulating rubber compound is subjected to electrical stresses and these stresses are suiiiciently high at any place in the insulation where the latter is in contact Awith air the air fails electrically, that is, becomes an electzical conductor. This condition is known in the electrical art as corona or ionization of the air.

15 This corona has the` property of attacking the rubber in contact with it and eventually results in an electrical breakdown or failure of the insulation. This action is progressive, the effect increasing as time goes on and the more intense the corona, the shorter the time necessary to cause failure of the insulation. While in actual practice the electrical stress may not be very high so that the time necessary to cause sufficient destruction of the insulation to result in failure 25 may be quite long, nevertheless deterioration is constantly going on and failure of the insulation will eventually result. Such a condition is objectionable and various means have been tried and are employed for overcoming this condi- 30 tion.

wrapped over the insulation in intimate contact therewith. In other cases a lead sheath has been employed over the insulation. Both of these methods, however, are not entirely satisfactory v in that bending of the cablecauses the tape or the lead sheath, as the case may be, to separate from the insulation causing an air pocket so that corona can take place. The metal covering referred to above is grounded so that there is a 40 grounding of the insulation throughout its length to conduct the charging current to ground.

My invention provides an improved construction in electric cables whereby grounding is readily accomplished, that is to say, the surface of 45 the insulation is brought to earth potential while at the same time the charging current is conducted to ground without the disadvantage of air pockets occurring at the surface of the insulation to cause corona.

50 In practice my invention provides a pliable conducting rubber compound which is applied over the rubber compound used as the electrical insulation. This compound instead of being an insulation, however, is an electrical conduc- 55 tor, that is to say, it has low electrical resist- For example, a metal tape has been ance so far as a rubber compound is concerned, although high in electrical resistance in terms of the resistance of the copper conductor oi the cable. This special rubber compound is capable of producing a grounding of the surface of the 5 electrical insulation, bringing the latter to earth potential, which is desirable, and at the same time is capable of conducting away the charging current of the insulation, thereby to prevent corona discharge. Various methods may be employed in the application of this conducting rub-` ber compound. For example, the compound may be applied as a layer directly in contact with the electrical insulation and vulcanized with the latter into a single solid compact mass, thus eifectually eliminating air or gases from the insulation surface. It may also be applied by frictioning it into cloth which in turn is applied as a tape wrapping or serving over the insulation. In this latter case the tape may be applied either before or after vulcanizing of the insulation.

In the accompanying drawing:

Figs. l and 2 show in elevation and section, respectively, an embodiment of my invention as applied to Va single conductor cable; and

Figs. 3 to 8, inclusive, show various modiiications of the construction of Figs. 1 and 2, my in- Avention in these latter iigures being applied to 'multiple-conductor cables.

Referring rst of all to Figs. 1 and 2, I desig- 30 nates the copper conductor ofthe cable. This conductor may be either of the solid design as illustrated or of the stranded design, this fea.- ture having no effect whatsoever on the invention.

2 designates a layer of rubber compound commonly used as electrical insulation in conductor cables. 3 designates a layer of conducting compound, the use of which constitutes the essence of this invention, this layer surrounding the in- 40 sulation 2 and being in intimate contact therewith throughout. 4 is the usual outer covering or sheath. This outer covering may be a lead sheath, a saturated braid, or a special highly abrasive resistant rubber sheath. When employv ing a saturated braid or an abrasive resistant rubber sheath as the outer covering, the conducting compound 3 is connected electrically to ground to carry oil the charging current.

In Figs. 3 and 4 I show my invention applied 50 to a multiple-conductor cable. In these iigures of the drawing, 5, 6 and 1 designate the conductors of the cable, each of these conductors being covered by insulation 2 similar to the insulation 2 of Fig. 1. The insulation 2 surround- 55 ing each of the conductors B, i and 'l has a conducting rubber compound applied thereto, as shown at 9, I0 and II, respectively. This conducting compound is similar to the conducting compound 3 of Fig. 2.

I2 designates a Jute or some such similar material employed as a nller to fill inthe interstices between the conductors so as to obtain a circular cross section. Il designates an outer lead sheath, such as shown in Fig. 1. If a high abrasive resistant sheath is substituted for the lead sheath, as referred to in connection with Fig. l, then a similar material may be employed as a nller in place of the Jute nller I2.

The electrical conductivity ofthe conducting compound 9, I0 and I I may be increased if desired by providing a bare wire Il in the center of the cable contacting with the compound as shown in Fig. 4.

In the form of my invention illustrated in Figs. 5 and 6 I show a construction similar. to that shown in Figs. 3 and 4, except that a binder tape designated I5 has been wrapped about the cable after ythe same has been built up and rthe outer sheath IB is applied over this tape. This binder tape will have the conducting rubber compound frictioned into the cloth of the tape. As in the case of the other forms of my invention above described the sheath IB may be lead, a saturated braid or a highly abrasive resistant rubber sheath, and as above mentioned, in the latter two cases at rthe ends of the circuit vthe conducting compound 9, III and II about each conductor is connected electrically to ground to carry oi the charging current.

In Figs. 'l and 8 I have shown the application of my invention to a submarine cable. In this connection .the use of my invention applies to the shore ends of the cable, that is to say, the parts that are not always submerged in water and the ends of the cable which are not in the ground. 'I'his construction, as will be apparent from an inspection of the drawing, is similar to the construction shown in Figs. 5 and 8 and similar reference characters have been applied thereto, but in this instance I apply a covering I1 of armor wire which is laid over the jute I9 which surrounds the tape Il, this jute having been substituted for the lead sheath l of Fig. 6, for example. v

Throughout the above description I have referred to the material applied to the electrical insulation of the cable as a conducting compound or as a conducting rubber compound and these expressions are to be interpreted as covering or including a material composed of metallic, mineral or other conducting particles or hygroscopic or deiiquescent substances :adhering to, admixed with or dispersed in a matrix, vehicle or binding material, constituting a solid, plastic or iluid composition capable oi' application to or uniting with rubber compounds or other flexible dielectrics.

The following materials are suggested as suitable conducting substances which may be employed:

Metallic powders, flakes or pigments;

Alloy powders, flakes or pigments;

Metaloid powders, flakes or pigments;

Dispersed mercury and amalgams;

Graphite, natural or artificial, and other forms of free carbon:

Deiiquescent and hygroscopic materials, organic or inorganic, liquid or solid;

Saleine matter or other electrolytes;

Electro-deposited metals, etc.

As above mentioned the conducting compound may be applied as a layer directly in contact with ythe insulation of the cable and vulcanized with the latter in a single compact mass or as an alternative it may be applied by impregnatlng it into cloth which :in turn is applied as a tape wrapping over the insulation, the tape being applied either before or after vulcanizing of the insulation.

In any event it is to be understood that my invention comprehends 4the application of a conducting compound to .the electrical insulation of the cable in such a manner that the formation of air pockets either in the manufacture of the cable or in bending the cable are eliminated, lthereby overcoming corona discharges, the charging current being conducted .to ground to bring the surface oi the electrical insulation to earth Potential.

In reference to the insulation about the conductor or conductors of :the cable, it is to be understood that this insulation need not be a rubber compound so far as this invention is concerned, inasmuch as varnished cambric, impregnated paper or other suitable insulation can be used equally well and my conducting material applied tothe outside of the same.

What I claim is:

1. An insulated conductor, comprising a conductor and vulcanized rubber insulation thereon, and a conducting covering over and in direct contact with said insulation comprising a textile base impregnated with a rubber compound including finely divided conducting material in such proportion as -to render said rubber compound conductive.

2. An insulated conductor, comprising a conductor and vulcanized rubber insulation thereon, and a conducting covering over and in direct contact with said insulation comprising a textile base impregnated with a rubber compound including graphite in such proportion as to render said rubber compound conductive.

3. An insulated conductor, comprising a conductor and vulcanized rubber insulation thereon, and a conducting covering over and. in direct contact with said insulation comprising a textile base impregnated with a rubber compound ncluding finely divided conducting material in such proportion as to render said rubber compound conductive, said conducting covering being vulcanized to said rubber insulation.

4. In combination an insulated conductor and a conducting covering over and in direct contact with the insulation of the said conductor, said conducting covering comprising a textile base impregnated with a rubber compound including finely divided conducting material in such proportion as to render said rubber compound conductive, said conductive covering being connected to ground.

5. In combination a conductor, vulcanized rubber insulation therefor and a conducting covering over and in direct contact with said insulation comprising a textile base impregnated with a rubber compound including finely divided conducting material in such proportion as to render said rubber compound conductive and an outer covering over said conducting covering.

6. In combination an insulated conductor and n a conducting covering over and in direct contact with the insulation of said conductor, said covering comprising a textile base impregnated with a rubber compound including finely divided conducting material in such proportion as to render said rubber compound conductive and a lead sheath over and in direct contact with said conducting covering.

7. In combination an insulated conductor and a conducting covering over and in direct contact with the insulation oi said conductor, said covering comprising a textile base impregnated with a rubber compound including nely divided conducting material in such proportion as to render said rubber compound conductive and abraided cover over said conducting covering.

8. In combination a conductor. vulcanized rubber insulation therefor, conducting covering over and in direct contact with said insulation, said conducting covering comprising a textile base impregnated with a rubber compound including finely divided conducting material in 9. In combination a conductor. vulcanized rubber insulation therefor, a conducting coverv ing over and in direct contact with said insulation, said conducting covering comprising a textile base impregnated with a rubber compound including nely divided conducting material in such proportion as to render said rubber compound conductive, a jute covering about said conducting covering, and armor wire wrapped about said jute.

ROBERT J. 

